CHAPTER 1 GROTZINGER,JORDAN PRESS

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CHAPTER 1 GROTZINGER,JORDAN PRESS SIEVER,
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Concepts you need to know for the quizzes and
exams

• The Scientific method
• Principle of Uniformitarianism
• Major chemical Composition of the Earth vs. crust
• Major layers of the earth

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Lecture Outline

• 1. What is Earth Science?
• 2. The scientific method
• 3. The geologic record
• 4. Discovery of a layered Earth
• 5. Earth as a system of interacting components

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Lecture Outline

• 1. What is Earth Science?
• 2. The scientific method
• 3. The geologic record
• 4. Discovery of a layered Earth
• 5. Earth as a system of interacting components

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• Earth Scientists study
• Rocks (Mineralogy)
• the earth (Geodynamics)
• the moon (Petrology)
• the physical evidence for the solar system
• chemistry of the solar system (Geochemistry)
• physics of earthquakes (Geophysics)
• past biology (Paleontology)

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The main difference between Earth Science and the
rest of the sciences (except for astrophysics) is
the use of DEEP TIME. For us a million years
passes like a 15-minute break. Geological
processes can take place more slowly than people
can notice. But because they run for extremely
long periods of time their effects are
great. Water recharge in Baton Rouge takes 1000
years Climate change has been accelerated by CO2
emissions over the past 100 years.
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Lecture Outline

• 1. What is Earth Science?
• 2. The scientific method
• 3. The geologic record
• 4. Discovery of a layered Earth
• 5. Earth as a system of interacting components

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The Scientific Method
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The Scientific Method

• A philosophical approach
• A deductive reasoning approach
• Starts with numbers trends.
• Patterns. i.e. OBSERVATIONS
• Explains observations using one or several
  reasons, i.e. HYPOTHESES
• Verification that the explanation works by many
  experts

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The Scientific Method

• If you know the answer already that is not
  science
• Science is an intellectual process
• Barriers to science are human e.g., greed,
  dishonesty, fear of change, hunger for power,
  cultural conditioning, politics ...

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Pre-scientific medicine
Humours yellow bile, black bile, phlegm,
blood Methods of treatment like blood letting,
forced vomiting and purges were aimed at
expelling a harmful surplus of a humour. They
were still in the mainstream of American medicine
after the Civil War. Other methods used herbs and
foods associated with a particular humour to
counter symptoms of disease, for instance people
who had a fever and were sweating were considered
hot and wet and therefore given substances
associated with cold and dry. (Wikipedia, the
free encyclopedia, 2006)
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Origin if the Moon- Science at work

• OBSERVATION The Pacific is large? Why so large?
• Charles Darwins great grandson hypothesized that
  the Moon came from the Pacific Ocean (HYPOTHESIS)

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Origin if the Moon- Science at work

• HYPOTHESIS TESTING
• Pacific Ocean is 70-200 my old
• Such an impact would have melted the earth
• and reset all radioactive clocks to 0 years old
  about 100 my after the melting.

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Nebular Hypothesis and the origin of our Moon

• Oldest rocks on the moon are 4.47 by
• A Mars-shaped bolide hit the earth about 4.5 by

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Formation of the Moon (about 4.5 billion years
ago)
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Lecture Outline

• 1. What is Earth Science?
• 2. The scientific method
• 3. The geologic record
• 4. Discovery of a layered Earth
• 5. Earth as a system of interacting components
• 6. Overview of geologic time

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Principle of Uniformitariansim
The present is the key to the past
James Hutton

• Natural laws do not change but rates and
  intensity of processes may vary.

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Examples of physical processes

• Radioactive decay
• Gravitational attraction
• Electromagnetic behavior

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Some Geologic Events are Slow
The Grand Canyon

• It took more than 250 million years to deposit
  this sequence of rocks.
• The rocks at the bottom of the canyon are about 2
  billion years old.

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Some Geologic Events are Rapid
Meteor Crater

• This feature (2 km across) formed in less than
  one minute about 50,000 years ago

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The chances that a bolide 1-2 km in diameter
will hit the earth by 2880 is 1300
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Martian ventifact (NASA)
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Rivers on Titan
NASA
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Some Geologic Investigations are Microscopic
1 mm
Features less than 0.1 mm can give important
information about the history of many rocks.
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Some Geologic Investigations are Microscopic
NASA
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Lecture Outline

• 1. What is Earth Science?
• 2. The scientific method
• 3. The geologic record
• 4. Discovery of a layered Earth
• 5. Earth as a system of interacting components
• 6. Overview of geologic time

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• Seismic waves illuminate Earths interior
• Compression and shear waves behave differently
  and are bent or absorbed at layer (chemical)
  boundaries within the Earth
• Earths interior is layered according to density
• Surface rock density is less than 3.5 g/cm3
• Whole Earth density is 5.5 g/cm3
• Core density must be about 8 g/cm3

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Composition of the Earth (70)

• Key earth elements in the crust Si, O
• Key earth elements in the earth Fe, Si, O

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Chemical Composition of Earth
Whole Earth FeOSiMg 93
Crust SiOAl 82
Fig. 1.7
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Crust
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Mantle
Crust
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Mantle
Crust
Liquid iron outer core
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Mantle
Crust
Liquid iron outer core
Solid iron inner core
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The crust continents are made of lighter rock
and thus literally float on material of higher
density.
0 (km)
Oceanic crust (3.0 g/cm3)
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Continental crust (2.8 g/cm3)
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Mantle (3.4 g/cm3)
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Moho discontinuity
Horizontal distance not to scale
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Less dense continental crust floats on
denser mantle.
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Composition of the Earth

• What is responsible for the distribution of light
  and dense elements by depth?
• How did they get there if the Earth was solid?

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Global Chemical Differentiation
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Lecture Outline

• 1. What is Earth Science?
• 2. The scientific method
• 3. The geologic record
• 4. Discovery of a layered Earth
• 5. Earth as a system of interacting components

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Earth as a Group of Interacting Systems

• Atmosphere, Hydrosphere, Lithosphere,
  Asthenosphere, Deep Mantle, Inner Core interact
• e.g. Volcanic degassing creates warm periods in
  Earths history
• The oceans buffer greenhouse gases
• The Cores magnetic field allows migration of
  fish and birds

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Major Components of the Earth System
Fig. 1.10
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END OF CHAPTER 1